Drilled discs are just bad...
If you push them hard they can crack or, at best, due to lower yield strength, warp quicker than a solid disc. If you combine them with fast road pads, they are no good as they actually cool down too quickly (a lot of fast road pads need to retain some heat in them to work - My Ferodo ones are a case in point). So either way, they just aren't ideal.
There is also potential for fast fracture as very small cracks can propogate quite quickly, depending on the quality of the material, and combined with already being weakened by the drilled holes, means that there is potential for them to fail spectacularly without warning.
ETTO and all that, and to be honest I think you'll be fine so long as you keep an eye on them, but I'm not sure I'd personally put vanity over performance, let alone safety. It's a bit like running Pilot Sport Cups all year round because they look the part.
And the reason they crack is not so much due to therman expansion, it's literally the stress applied to them under braking. Removing material vastly weakens an already quite brittle metal.
